In the past two decades, tremendous advances have been made in understanding the molecular mechanisms used by various types of cell surface receptors to transduce signals. Nearly all of these advances have come from the study of model systems where a receptor xe2x80x9cactivatesxe2x80x9d cells to generate a well-defined response. As knowledge about activating model systems has increased, it has become clear that there are many situations in which the activating signal sent from one receptor is modulated as the direct result of a negative or inhibitory signal sent by another cell surface receptor. While the study of this type of signaling is generally in its infancy, several recent studies have begun to shed light on the molecular mechanisms which underlie receptor-mediated inhibitory signals in immunologic systems. Given the tendency of nature to utilize signaling functions modularly in a variety of signaling pathways, the paradigms outlined by these systems may have implications for the study of inhibitory or deactivating signals in non-immunologic situations as well. In addition, the study of these signals may add new dimensions to the understanding of other widely utilized signaling pathways.
As described herein, monoclonal antibodies (mAbs) have been isolated which inhibit Fcxcex5RI-induced mast cell degranulation. Through protein isolation, peptide sequencing, cloning, and gene expression, CD81 has been identified as a novel inhibitory receptor for Fcxcex5RI and Fcxcex3RIII. Anti-CD81 mAbs also inhibited passive cutaneous anaphylaxis (PCA) reactions, a model of IgE-dependent, mast cell activation in vivo.
The invention pertains to a method of inhibiting cell surface receptor-mediated signaling comprising contacting a cell with an agent which induces CD81-mediated signal transduction. In a particular embodiment, the cell surface receptor is selected from the group consisting of Fcxcex5RI and Fcxcex3RIII. In one embodiment, the method is a calcium independent method.
The invention also relates to a method of inhibiting degranulation comprising contacting a cell with an agent which induces CD81-mediated signal transduction. In one embodiment, degranulation is mediated by the Fcxcex5RI receptor. In another embodiment, the method is a calcium independent method.
The invention further relates to a calcium independent method of inhibiting cell surface receptor-mediated signaling in a mammal, such as a human, comprising administering to the mammal an effective amount of an agent which induces CD81-mediated signal transduction. In one embodiment, the cell surface receptor is selected from the group consisting of Fcxcex5RI and Fcxcex3RIII.
The invention also pertains to a method, e.g., a calcium independent method, of inhibiting degranulation induced by a cell surface receptor-mediated signal in a mammal, such as a human, comprising administering to the mammal an effective amount of an agent which induces CD81-mediated signal transduction.
The invention further pertains to a method of treating (e.g., preventing or reducing the severity of) an allergic condition in a mammal, such as a human, comprising administering to the mammal an effective amount of an agent which induces CD81-mediated signal transduction. In particular embodiments, the allergic condition is asthma, hay fever or atopic eczema.
The invention also relates to a calcium independent method of enhancing cell surface receptor-mediated signaling, e.g., Fcxcex5RI-mediated signaling and Fcxcex3RIII-mediated signaling, comprising contacting a cell with an agent which inhibits CD81-mediated signal transduction.
The invention also pertains to a calcium-independent method of enhancing degranulation comprising contacting a cell with an agent which inhibits CD81-mediated signal transduction. For example, degranulation can be mediated by the Fcxcex5RI receptor. The invention also relates to a calcium independent method of enhancing cell surface receptor-mediated signaling in a mammal comprising administering to the mammal an effective amount of an agent which inhibits CD81-mediated signal transduction.
The invention further relates to an assay for identifying agents which alter CD81-mediated signal transduction, comprising combining a cell bearing CD81 with an agent to be tested, under conditions suitable for CD81-mediated signal transduction, and determining the level of CD81-mediated signal transduction. If the level of CD81-mediated signal transduction is altered relative to a control, the agent alters CD81-mediated signal transduction. In a particular embodiment, the agent is one which enhances or induces CD81-mediated signal transduction.
The invention also relates to an assay for identifying agents which alter calcium independent CD81-mediated regulation of cell surface receptor signaling, comprising combining a cell bearing CD81 and an appropriate cell surface receptor with an agent which alters CD81-mediated signal transduction under conditions suitable for signal transduction by CD81 and the cell surface receptor, and determining the level of cell surface receptor signaling. If the level of cell surface receptor signaling is altered relative to a control, the agent alters calcium independent CD81-mediated regulation of cell surface receptor signaling.